A consultant's report commissioned by Tandberg said on Monday Cisco's $3 billion takeover bid for the Norwegian video conferencing equipment maker was fair.
Some Tandberg shareholders have said the offer is too low.
It is normal for Norwegian companies to seek a fairness opinion from an outside consultant before any major takeover deal is carried out.
It is of our opinion that the terms of the offer are fair from a financial point of view, so far as the shareholders of Tandberg as concerned, Ernst & Young said in the report.
Sources told Reuters last week that Cisco Systems was mulling various options, including withdrawing its bid or raising it, after a group of Tandberg shareholders looked set to block the deal unless its terms were sweetened.
The takeover, which needs approval from 90 percent of Tandberg shareholders, has been approved by Tandberg's board.
A group of shareholders holding nearly a quarter of Tandberg shares have snubbed the offer.
In the apparent absence of alternative offers, Tandberg shares have fallen below the Cisco bid price of 153.50 crowns after trading above it for weeks.
At 1047 GMT (5:47 a.m. EST), Tandberg stock traded at 153.00 crowns, down 0.5 percent in line with Oslo's .OSEBX index.
(Reporting by Oslo newsroom)